The present invention relates to a method of measuring the number of times of a specific behavior, such as scratching, of a small animal, e.g., mouse in a breeding cage noninvasively, and an automatic measuring instrument for it.
Physiological or pharmacological researches have conventionally been made with the behavior of small animals such as mice as an index. For measurement of changes in the behavior, usually employed are visual observation, video recording, rotatable cage and the like. Particularly in the pharmacological researches of the scratching behavior of mice or rats to which a medicament inducing scratching has been administered, visual observation or observation using a recorded video is frequently employed, though the observation time is as short as 30 to 60 minutes.
Visual observation or observation through a recorded video is however accompanied with the problem that it requires not only labor but also time for acquiring data and in particular, success in observation through a recorded video depends on the position of a camera. An apparatus such as rotatable cage, on the other hand, involves the problem that animals are exposed to an excessive stress when placed under a special environment.
Various mice who spontaneously develop dermatitis and always display a scratching behavior have recently been found and their use for discovery of a scratching mechanism or searching of a new medicament is just started. In studies using such mice, observation over long hours becomes necessary and there is consequently a strong demand for the development of automatic measurement. An instrument for measuring scratching times by attaching a ring to the hind leg of such a mouse and measuring the movement of the leg through a magnetic sensor has recently been put on the market.
Small animals such as mice are forced to be under an unnatural state in such a measuring instrument and it takes long hours for them to get accustomed to the state. In addition, only the movement of the site to which the ring has been attached can be measured by such an instrument.
In consideration of the conventional problems and actual situations as described above, the present invention has been made. An object of the invention is to provide a method for measuring the number of times of a specific behavior, such as scratching, of small animals, e.g., mice in a breeding cage noninvasively; and an automatic measuring instrument for it.
With a view to attaining the above-described object, the present inventors have carried out an extensive observation and investigation on a change occurring when a mouse makes a move in a breeding cage. As a result, it has been found that the vibration of the cage due to the specific behavior of the animal shows a peculiar frequency and strength pattern, leading to the completion of the invention.
The above-described object is attained by a method of measuring the number of times of a specific behavior of an animal in a breeding cage, which comprises a first step of detecting vibration of the cage caused by the specific behavior of the animal as an electrical signal, extracting the feature of a frequency component of the signal and determining a common pattern of the frequency and strength of the specific behavior of the animal;
a second step of detecting, as an electrical signal, vibration of the cage caused by all the behaviors of the animal in the breeding cage within a certain time, extracting the feature of a frequency component of the signal and determining a measurement objective pattern of the frequency and strength of all the behaviors of the animal; and
a third step of comparing the common pattern obtained in the first step with the measurement objective pattern obtained in the second step, and counting the number of the common patterns existing in the measurement objective patterns.
The above-described object is also attained by an automatic measuring instrument of the number of times of a specific behavior of an animal in a breeding cage, which comprises:
means for detecting vibration of the cage caused by the behavior of the animal as an electrical signal,
means for extracting the feature of a frequency component of the signal thus detected, and
means for comparing a common pattern of the frequency and strength thus extracted with a measurement objective pattern and counting the number of common patterns in the measurement objective patterns.